Various methods have been conventionally studied to detect trajectory data different from the others from large quantities of trajectory data in traffic field, or to detect a trail pattern different from the others from a great deal of operation trail logs in BPM (Business Process Management) field.
The above described detection may be achieved by a method that represents trajectory data or tail log with sequential data that defines an order of items, and detects abnormal sequential data based on appearance frequencies of sequential patterns that are combinations of items appearing in the sequential data as disclosed in R. Agrawal and R. Srikant, Mining Sequential Patterns, IEEE '95 (Non-Patent Document 1).